Q1 of 108 Page 42

Solve the following quadratic equations by the method of completing the square:

4x2 + 3x + 5 = 0


Now in the above quadratic equation the coefficient of x2 is 4. Let us make it unity by dividing the entire quadratic equation by 4.

x2 – 3/4x + 5/4 = 0


x2 – 3/4x = -5/4


Now by taking half of the coefficient of x and then squaring it and adding on both LHS and RHS sides.


Coefficient of x = 3/4


Half of 3/4 = 3/8


Squaring the half of 3/4 = 9/64



Now the LHS term is a perfect square and can be expressed in the form of (a-b) 2 = a2 – 2ab + b2 where a = x and b = 3/8



On simplifying both RHS and LHS we get an equation of following form,


(x ± A)2 = k2



It is observed that the term obtained on RHS is a negative term and taking square root of a negative term will give imaginary roots for the given quadratic equation.


Therefore the given quadratic equation does not has real roots.


More from this chapter

All 108 →